More on visual structure
To say that ‘visual structure is the way the eyes perceive physical structure’ (as we did here) suggests a one-on-one relationship between the two. It’s not as simple as that. Perception involves a complicated chain of events from light entering the eye, being registered an processed in it, traveling through the optic nerve, being transformed into electrical impulses which travel along different routes by way of chemical transmission between brain cells, forming tentative images which are being checked and adjusted through comparison with images stored in memory, until in the end an image is formed and interpreted. So: what we see is not necessarily a picture of what is ‘out there’.
An awe-inspiring example of the intricate ways visual structure can be perceived, are famous studies about the perception of Japanese rock gardens. (See two articles, one with a link.)
Miura, Kayo & Haru Sukemiya, ‘Visual Impression of Japanese Rock Garden (Kare-sansui): From Point of View of Spatial Structure and Perspective Cues.’ In: Proceedings of International Symposium on EcoTopia Science 2007, ISETS07 (2007) (Link)